Now \(\mathbf {\phi }_{\mathrm {r}}^{(t+1)}\)  belongs to \(\mathcal {C}^{M}\) , which satisfies the unit constant modulus constraint.
The details of the Riemannian-manifold algorithm are presented in Algorithm REF  and the computational complexity is approximated by \(\mathcal {O}(M^{2})\)  [1]}, [2]}.
